Monoclonal antibodies directed against the human A431 β‐adrenergic receptor recognize two major polypeptide chains

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Abstract
A serum-albumin-alprenolol conjugate was used to isolate .beta.-adrenergic receptors from the human A431 cell lysates. Three monoclonal antibodies were obtained from BALB/c mice immunized with these receptors. These antibodies: BRK-1, BRK-2, BRK-3, were respectively of the IgM, IgG2a and IgG3 classes. All three antibodies recognized photoaffinty-labelled receptors, immunoprecipitated ligand-binding activity and identified the 65-kDa and 55-kDa polypeptides corresponding to the .beta.2-adrenergic receptors of A431 cells, BRK-2 and BRK-3 recognized both .beta.1 and .beta.2-adrenergic receptors of several mammalian cells. All three antibodies visualized, by immunofluorescence, the .beta.2-adrenergic receptors at the surface of A431 cells. The monoclonal antibodies are directed against the protein portion of the .beta.-adrenergic receptors since partial or complete removal of the carbohydrate moieties by treatment with endoglycosidase such as endo-F (endo-.beta.-N-acetylglucosaminidase F) and peroxidate oxidation did not affect the immunoreactivity. These antibodies will be of value to immunopurify the .beta.-adrenergic receptors.